Apparatus for the continuous casting of metals



United States Patent [72] Inventor Alfred J. Wertli, 2,284,703 6/1942 Welblund et al l64/282X Poststrasse 15, 8406 Wlnterthur, 2,667,673 2/1954 Harrison l64/282X Switzerland 3,290,734 12/1966 Wertli [64/282 [2]] Appl. No. 660,280 3,314,115 4/1967 Saunders et al. l64/282 [22] Filed Aug. 14,1967 3,338,140 8/1967 Sheesley 74/89.]7X [45] Patented Nov. 17, 1970 3,398,780 8/1968 Yearley l64/83X I 21 Priority g- 12, 1966 FOREIGN PATENTS I331 706,802 3/1965 Canada l64/282 [3 I] 11,714/66 895,913 5/1962 Great Britain l64/232 i Primary Examiner-J. Spencer Overholser APPARATUS FOR THE CONTINUOUS CASTING Assistant Examiner-R. Spencer Annear 0F METALS Anorney- Kenyon & Kenyon, Reilly, Carr & Chapin 6 Claims, 3 Drawing Figs.

[Sl] IILCI. B22d 11/12 [50] Field Search l64/82, 83, ABSTRACT; The cast strand is advanced away f om h f r. 283; 74/29 33, 8917 nace mold by pairs of gripping rollers which alternately grip and feed the cast strand. At least one roller of each pair of [56] References cued gripping rollers is driven by a hydraulic system in an intermit- UNITED STATES PATENTS tent manner to advance the strand in a series of small increl,277,000 8/l9l8 Turner 74/89. 1 7X ments at a high rate to obtain a homogeneous structure.

Patented No v. 17, 19'70 Sheet 1 of 2 Inventor: ALFRED d. Wear/.1

147'70 Eys Patented Nov. 17 1970 Z of 2 Sheet Inventor: ALFRED d. Wen-r1.

stances, the drive for the gripping rollers which has generally.

consisted of an electric motor or of an electric motor with an electromagnetic clutch has been switched off after each forward movement of the strand and then switched on again to impart a further forward movement to the strand. However, because of the long time constants involved in the starting and stopping of the motor or the engagement and disengagement of the electromagnetic clutch, these heretofore methods have been able to permit only relatively few strokes per minute, for example, less than 40.

Since it has been found that the shorter the stroke and the more often the strand is advanced in a unit time, the more homogeneous the structure of the cast strand becomes, it is desirable to effect a considerable increase in the number of strokes per unit time. Further, if possible, thelength of the stroke should be less than the smallest dimension of the cross section of the strand to be cast.

Accordingly, it is an object of the invention to increase the rate of strokes per unit time of a cast strand under the influence of pairs of gripping rollers.

lt is another object of the invention to dispense with an electric motor or an electric motor having an electromagnetic clutch for driving the gripping rollers of a continuous casting apparatus.

It is another object of the invention to advance a continuously cast strand in a series of shortintermittent strokes at a relatively high rate of strokes per unit time.

It is another object of the invention to obtain a cast strand of metal of homogeneous structure.

Briefly, the invention provides a method and apparatus for moving a cast metal strand in a generally'horizontal plane in a series of short intermittent strokes at a relatively high rate of strokes per unit time under the influence of pairs of gripping rollers in order to achieve a more homogeneous cast structure than heretofore achieved by gripping rollers.

The method of the invention involves the advancement of the cast strand from the mold of a furnace of know construction in a forward intermittent manner under the influence of at least two pairs of gripping rollers. With one of the pair of gripping rollers in gripping engagement with the cast strand, the rollers are actuated to move the strand forwardly in one or more feed movements without being released between individual movements. Subsequently, with the first pair of rollers being released from gripping engagement with the strand, another pair of gripping rollers grip the strand and move the strand forwardly in one or more feed movements without being released from the strand between movements. Thereafter, the pairs of gripping rollers continue to operate in sequence to alternately grip and move the strand continuously forwardly in successive feed movements. The strand can be fed forwardly by one pair ofgripping rollers in one long stroke or several short strokes before the other pair of gripping rollers feeds it forwardly through one long stroke or several short strokes. The travel of the strand made in one long stroke or several short strokes under the action of one pair of gripping rollers before release of these gripping rollers is made great enough to enable the other pair of gripping rollers to feed the strand forwardly. This method enables a strand to be cast at considerably higher speeds of casting than hitherto, for example, at 200 to 300 strokes a minute with each stroke being only l to 20 mm. long. Thus, the strand has a fine very uniform structure.

The apparatus of the invention includes at least two pair of gripping rollers which are disposed to grip and move the strand forwardly away frorri the mold of a furnace. Each pair of gripping rollers includes at least one roller which is driven such that one pair of gripping rollers is pressed against the strand to impart one or more feed strokes to it while the other pair of gripping rollers is released from gripping engagement with the strand. The drive for the gripping rollers is constructed so as to effect in a simple manner a variation not only in the time of motion and rest within each individual cycle but also in the length of each cycle. Also, any variation in the length of a cycle and in the times of motion and rest within each cycle can be carried out while the apparatus is'in operation. Thus, the apparatus can be advantageously suited in operation to suit the characteristics of the pure metals and alloys that are to be cast. Likewise, the apparatus is suited to feed a cast strand forwardly in a continuous manner.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 diagrammatically illustrates an apparatus of the invention,

FIG. 2 diagrammatically illustrates the invention; and

FIG. 3 graphically illustrates the intermittent movement of a cast strand as a function of time according to the invention.

Referring to FIG. I, a furnace 1 is provided with one or more molds 2 which are surrounded by a cooling device 3 in a known manner. A pair of withdrawal units 4, 5 eachof which consists of two pairs of gripping rollers, are positioned downstream of the mold 2 to cooperate with the furnace structure.

. In operation, molten metal in the furnace l flows into the mold 2, is solidified into a cast strand 6 in the mold 2 by the cooling device 3 and leaves the mold 2 in the direction indicated by the arrow 7. After passing through the two withdrawal units 4, 5, the strand fipasses onto a roller strand (not shown).

The withdrawal units 4, 5 are made of similar components which are indicated by like reference numerals in the drawings, primed reference numerals being used in withdrawal unit 5. The withdrawal unit 4 includes a pair of gripping rollers which consist of upper gripping rollers 8 which are pressed against and released from the strand 6 by a suitable means such as, hydraulic devices containing pistons 34, 34' acted on by pressure medium, or by electrical or pneumatic devices (not shown), and lower gripping rollers 9 which are'driven. Each lower gripping roller 9 is connected to a a modified apparatus of pinion 27 through a spindle 26 in a suitable manner such that rotation of the pinion 27 causes rotation of spindle 26 and consequently rotation of roller 9. The pinions 27 both mesh with a toothed rack 28 which is connected on one end (to the right end as shown in FIG. 1) to a piston 10 which is mounted in a cylinder 1 l for reciprocation relative to the cylinder 11. A pipe 12 is connected to the right-hand end, as viewed, of the cylinder 11 for feeding of a pressure medium into the cylinder 11 under the control of a changeover valve 13 connected to the other end of the pipe 12. In addition, another pipe 14 which forms a part of a separate pressure medium feed system (not show) is connected to the cylinder 11 for the passage of a pressure medium therebetween. The changeover valve'13 is also connected by a pipe 12' to a cylinder 1 1' and a pipe 14' of the separate pressure medium feed system is connected to the cylinder 11'. A switch 15 is positioned in the path of the toothed rack 28 at the limit of travel to cooperate with a striker l6 fitted to the rack 28. Actuation of the switches 15, 15 control the actuation of the changeover valve 13.

The means constituted by the hydraulic devices connected to each of the pairs of gripping rollers 8, 8' serve to alternately press and release each pair of gripping rollers 8, 8' onto and from the cast strand 6 in alternating manner. In this regard, the pistons 34, 34 are acted on by the pressure medium such that as one set of pistons 34 are pressed against the strand 6 the other set of pistons 34 are lifted from the strand 6.

Pressure medium is pumped by a pump 17 from a reservoir 18 and fed to the changeover valve 13 by way of a valve 19 and a flow regulator 20. The changeover valve 13 thus directs the pressure medium into one or the other of the feed pipes l2, 12. For example, for the shown positions, pressure medium is fed to the cylinder 11 via pipe 12 under a pressure, for example, of 50 kp./sq.cm. so as to drive the piston in a direction opposite to that indicated by the arrow 7. The rack 28 thus acts through the pinions 27 to rotate the gripping rollers 9 clockwise, as viewed. Since the gripping rollers 8 are pressed against the strand 6 during this rotation of gripping rollers 9, intermittent motion is imparted to thestrand 6 in the direction indicated by the arrow 7. During this time, the pressure in the pipe 14 is maintained at a lower value, for example, 10 kp./sq.cm. than in pipe 12 so that the pressure medium in this system is driven out ofthe cylinder 11. In addition, during this movement of piston 10, the piston 10 is driven by the' pressure medium in the pipe 14' in the direction indicated by the arrow 7 to be brought into starting position. However,

gripping rollers 8', as indicated by the broken line arrows, are

released from engagement with the strand 6. The pressure medium on the right of the piston 10' as viewed escapes through a suitable pipe (not shown) and returns to the reservoir 18.

When the striker 16 on the rack 23 operates the switch 15, the strand 6 having been fed forwardly intermittently, for example, 20 to times, the changeover valve 13 is changed over so that the pressure medium fed by the pump 17 now passes through the pipe 12' into the cylinder 11. This piston 10 then imparts a number of successive intermittent movements to the rack 28 in a direction opposite to that indicated by the arrow 7. At the same time as the valve 13 is changed over, the gripping rollers 8' are pressed on to the strand 6 while the gripping rollers 8 are released from the strand 6. The piston 10 is thereupon returned to the starting position by the pressure medium in the pipe 14 in a manner as described above in regard to the piston 10.

The amount of pressure medium which is fed to the piston 10 or 10' performing work is regulated with the aid of the flow regulator 20. Also, the intermittent motion of the respective pistons 10 or 10 is regulated by the valve 19 which is periodically opened and closed by means of a rotatable cam 21. The cam 21 is driven by a motor (not shown) through a variable speed gear (not shown).

Referring to FIG. 3, varying the speed of the gear operably connected to the cam 21 varies the length of a cycle 7 while substitution of a differently shaped cam for cam 21 alters the times of motion and rest within each cycle. For example, the ratio B/R of motion/rest can be changed from I 2 to a B'lR of 3 l. Further, by replacing cam 21 with a disc ofa cylindrical periphery, continuous movement of the withdrawal units 4 and Sis obtained.

Alternatively, instead of using cam-operated valve 19, a

magnetic valve which is operated by an electrical or electronic pulse generator can be used. Such a pulse generator similarly offers a simple means of varying the length of the cycle and the times of motion and rest ofthe withdrawal units.

Referring to FIG. 2, a strand 6 which is in strip form is withdrawn from a furnace in the direction indicated by the arrow 7. For this drawing action, two withdrawal units are provided, each with a pair of gripping rollers, 8/9 and 8'/9' respectively, driven in the same way as in FIG. 1, namely by pistons 10 and 10, which through a rack 28 or 28' and pinion 27 or 27 rotate the lower rollers 9 and 9' respectively. This arrangement differs from that shown in FIG. 1 in that the pressed against the strip 6, and the lower roller 9 is feeding the strip forwardly. The upper roller 8', on the other hand, is

raised from the strip by the piston 34' and the lower roller Q is at rest, since the associated piston 10' is in its starting position.

- piston 10 is returned to its starting position from the leftward position shown in FIG. 2.

It is noted that both the upper and lower gripping rollers of each pair of gripping rollers can be modified so that both are placed under pressure for engagement with the strand. Also, the upper roller in each pair can be modified so as to be driven in a manner similar to the lower roller.

Iclaim:

1. An apparatus for horizontally continuously casting metals comprising:

a furnace,

a mold connected to said furnace for molding a cast strand from molten metal within said furnace;

at least two pairs of gripping rollers disposed downstream of said mold for gripping the cast strand and for advancing the gripped strand away from said mold;

means connected to at least one roller of each of said pair of gripping rollers for driving said one roller, said means including a cylinder, a piston reciprocally mounted in said cylinder, means operably connected between said. piston and said one roller for rotating said one roller upon reciprocation of said piston, a pressure medium feed system for conducting pressure medium into and out of said cylinder to reciprocate said piston therein and a common changeover valve connected to each pair of gripping rollers for alternating the feeding of pressure medium between said pressure medium feed systems; and

means connected to each of said pairs of gripping rollers for alternately pressing and releasing each said pair of gripping rollers onto and from the cast strand in alternating manner whereby pressing of one pair of gripping rollers serves to advance the cast strand from said mold while the other of said pair of gripping rollers is released from the cast strand.

2. An apparatus as set forth in claim 1 wherein said means between said piston and said one roller includes a rack at one end of said piston outside said cylinder and a pinion rotatably connected to said'rack for rotation upon reciprocating movement of said piston and operably connected to said one roller for rotating said one roller upon reciprocating movement of said piston.

3. An apparatus as set forth in claim 2 further comprising a switch mounted in the path of each said rack at the limit of travel of each said rack for actuation thereby, said switch being connected to said changeover valve for changing over the feed of pressure medium through said changeover valve upon actuation thereof.

4. An apparatus as set forth in claim 1 wherein said pressure medium feed system includes a device for regulating the amount of pressure medium fed to a respective one of said cylinders.

5. An apparatus as set forth in claim 1 which further comprises another pressure medium feed system connected to said cylinders for acting on said pistons therein to return said piston to an initial starting position.

6. An apparatus as set forth in claim 1 wherein said piston for each pair of gripping rollers is disposed on the opposite side of a strand to be gripped from said piston for the other pair of gripping rollers. 

